1. Field of the Invention
The present invention generally appertains to new and novel improvements in heat exchangers and more particularly relates to a novel and improved heat exchanger especially suited for use as a marine keel cooler.
2. State of the Prior Art
The present invention is an improvement on marine heat exchangers for use as keel coolers and attendant systems as disclosed in my prior U.S. Pat. Nos. 2,258,526 and 3,177,936 and also as disclosed in U.S. Pat. No. 3,561,524.
Generally, such keel coolers include a header which is vertically partitioned into two separate chambers and which is fixed on the underside of the hull and is connected through the hull to the water or coolant circulating pump of the inboard marine engine. The chambers of the header are connected by longitudinally extending heat exchange tubes to a return fitting which is mounted on the underside of the hull and is longitudinally spaced from the header. The tubes are generally finned or fluted cooling tubes with the purpose of the fins being to achieve a decrease in the necessary lengths of the cooling tubes while at the same time increasing the heat exchange capacity of the tubes.
In operation, the heated water for the inboard marine engine or other equipment being cooled, such as accessory equipment, is pumped through one chamber of the header so as to flow through the tubes where it is cooled before it is recirculated from the return fitting through the tubes back to the other chamber of the header and the marine engine or other equipment being cooled. In this way, a closed cooling system is realized whereby the engine is completely closed off from the raw water in which the boat travels and whereby such raw, sandy and muddy water cannot grind up the circulating pump or build up in the engine water jackets. Also with the partitioned header only one opening need be made in the boat hull with the heated water passing through one chamber from engine to cooling tubes and returning to the engine after being cooled through the other chamber.
One of the difficulties attendant with such conventional marine keel coolers, as those disclosed in my afore-mentioned patents, resides in the fact that the desirability is to increase the heat exchange capacity of the tubing and attendant keel cooling system while decreasing the structural capacity and mounted extent thereof on the hull.
In my prior U.S. Pat. No. 3,177,936 means was disclosed whereby a new form of tubing could be used so as to shorten the length and decrease the diameter of the tubing while still developing greater heat exchange capacity. This was most efficient having regard to the longitudinal extent of the hull of a boat. However, the problem remained of the width or transverse capacity of the hull having in mind the specified coolant volume capacity of a given water circulating pump for a marine engine or accessory equipment mounted within the hull.
For example, a marine engine equipped with a 11/4 inch water circulating pump requires a keel cooler of one and a quarter inch volume capacity and a two tube cooler with one tube carrying the circulating heated water from the header to the return fitting and the other tube bringing the cooled water from the return fitting back to the header. The tubes are of the axially fluted or finned nature, as disclosed in my U.S. Pat. No. 3,177,936, and have an outside diameter of 11/2 inches with an inside square area of 1.223 and carry a liquid volume equal to a 11/4 inch pipe.
Continuing with the foregoing example, the next larger commercial pump available is a size 11/2 inch which requires a 11/2 inch tube flow or an area of 1.76 square inch to handle the volume so that a two tube cooling system with a single tube flow from header to return fitting and from return fitting back to header is inadequate. If an attempt to solve the problem is made by using a dual flow four tube cooling system whereby two tubes carry the flow from the header to the return fitting and two other tubes carry the return flow from the return fitting to the header then this will be a system that can handle a flow volume of 2.43 square inches which results in an oversized cooling system that has a reduced flow. And such oversized cooling system and attendant reduced flow results in higher costs and less heat exchange.